Effect of a food additive in the control of the acanthocephalanNeoechinorhynchus buttneraeinColossoma macropomum

Abstract

Neoechinorhynchus buttnerae is the only acanthocephalan species that has been detected infecting tambaqui (Colossoma macropomum) in northern Brazil. This helminth greatly affects nutrient uptake in fish and leads to cachexia and economic losses of up to 100% in tambaqui production. This study investigated the efficacy, in vitro and in vivo, of a food additive (Acantex) to control N. buttnerae in tambaqui, as well as its effects on fish blood parameters and possible effect on monogeneans. For the in vitro assay, the parasites were exposed to nine concentrations (1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 mg/kg) of Acantex and one control (without the product). For the in vivo assay, 120 naturally infected tambaqui were distributed into twelve tanks (10 fish per tank) and were divided into four treatments, in triplicate. Fish were fed with commercial feed containing 0.0, 3.0, 4.0 and 5.0 mg/kg of Acantex, for 25 days. Acantex at 3.0 mg/kg showed 100% efficacy against N. buttnerae in in vitro testing, after exposure for 2 hr. In vivo efficacy was 13.46% at 3.0 mg/kg against the endoparasite N. buttnerae and caused a mortality rate of 19%–37% of monogeneans. Blood and biochemical parameters suggested that fish were malnourished due to attached intestinal parasites and the resulting competition for nutrient uptake. Acantex did not show adequate efficacy in treating acanthocephalosis under the conditions of this study; therefore, more efficient forms of Acantex administration in the diet of tambaqui are warranted to eliminate acanthocephalans.